using System;
using System.Collections.Generic;

namespace RegistrationLogin
{
    class Program
    {
        static List< User> users = new List< User>();

        static void Main(string[] args)
        {
            Console.WriteLine("Select an option:");
            Console.WriteLine("1. Register");
            Console.WriteLine("2. Login");
            Console.Write("Enter your choice: ");
            int choice = int.Parse(Console.ReadLine());

            switch (choice)
            {
                case 1:
                    Register();
                    break;
                case 2:
                    Login();
                    break;
                default:
                    Console.WriteLine("Invalid option. Try again.");
                    break;
            }
            Console.ReadLine();
        }

        static void Register()
        {
            Console.Write("Enter your username: ");
            string username = Console.ReadLine();
            Console.Write("Enter your password: ");
            string password = Console.ReadLine();

            User user = new User(username, password);
            users.Add(user);
            Console.WriteLine("Registration successful.");
        }

        static void Login()
        {
            Console.Write("Enter your username: ");
            string username = Console.ReadLine();
            Console.Write("Enter your password: ");
            string password = Console.ReadLine();
            
            
      foreach (User user in users)
            {
                if (user.Username == username && user.Password == password)
                {
                    Console.WriteLine("Login successful.");
                    return;
                }
            }
            Console.WriteLine("Login failed.");
        }
    }

    class User
    {
        public string Username { get; set; }
        public string Password { get; set; }

        public User(string username, string password)
        {
            this.Username = username;
            this.Password = password;
        }
    }
}